Electrophysiologic Studies
Transmembrane action potentials (APs) of PVs, SVC, RA, and LA were recorded by machine-pulled quartz glass microelectrodes filled with 3 M KCl (resistance of 10-20 M Ω) connected to an amplification system. Two bipolar silver stimulating electrodes were attached to each preparation in the tissues. Recording sites were located 4 mm from stimulating electrodes. Transmembrane APs were digitized with an analog-to-digital converter and stored to a PC for subsequent analysis. Preparations were stimulated at a basic cycle length (BCL) of 1000ms during the equilibration period (0.5 h). Regular pacing was achieved by bipolar silver electrodes attached to each preparation (1-3ms duration period and 2.5 times diastolic threshold intensity). Isoproterenol (1uM) combined with high calcium (5.4mM) was used to induce DADs and triggered activity in PVs, SVC, RA and LA preparations before and after exposure to Triarylmethane-34(TRAM-34, a selective antagonist of KCa3.1, HY-13519, Med Chem Express, USA). TRAM-34 was dissolved in dimthyl sulfoxide to form a solution of 5uM concentration. Isoproterenol was dissolved in distilled water to form 1uM solution.